Method,apparatus and extrusion nozzle for producing a member from extrudable material

ABSTRACT

The method and apparatus for producing members (4) of extrudable material, for example a ceramic or synthetic plastic material, use a nozzle (2) composed of a plurality of segments (21 to 25) abutting without gaps and having extrusion ducts (28), segments (21, 22) of the nozzle being moved relative to one another, for example transversely relative to the direction of extrusion. With this method and apparatus it is possible to produce in a single operation members of which the structures, such as open ducts (40), change their relative positions and cross one another.

The invention relates to a method apparatus for producing a member fromextrudable material, and to members produced by the method.

Extruder plants are used to produce members from extrudable orcontinuously castable material, for example ceramic or synthetic plasticmaterial, etc. The molded members are, in the case of ceramics, alsofired or baked to preserve the final shape and strength of the ceramicmaterial of the articles. In chemical processing, for example catalysis,extruded members with a parallel duct structure are termed monoliths.

These are produced in extruder plants in which the ducts in an extrudernozzle do not change position relative to one another.

Plants using known methods can in fact produce members with ductstructures which are, for example, twisted spirally, but the relativepositions of the ducts to one another remain the same. All the ducts,however, always adjoin the same ducts, so that the variety of memberstructures available is very limited. DE-OS 25 27 787 also discloseshoneycomb extruded parts having a large number of narrow closed passageducts which may also partly not run parallel. Here again, there cannotbe any exchange between the individual closed ducts. For manyapplications, however, members with mutually crossing and open ducts arenecessary or advantageous wherever the medium carried, for example agas, a liquid, a free-flowing solid or a mixture, is to be mixed asthoroughly as possible or homogenised and at the same time directedoutwards from the interior of the member, for example in order to heator cool the flowing medium on the outside walls of a column and, inparticular, for optimal uniform and complete progress of the requiredreactions, mass transfer and changes of state in chemical reactioncolumns, mixers and catalyst systems. In such cases it is necessary forthe entire contents of all the ducts to be completely and uniformlycontinually re-mixed over the entire crosssection of a member. This,however, is generally impossible with closed ducts of arbitrary shape.

Member structures with e.g. mutually crossing ducts have previously beenmade by subsequently assembling a plurality of, for example, extrudedparts made from ceramic or plastic material. The additional operation ofsubsequent connection and e.g. bonding or re-baking of the connectionpoints, alone, demands considerable effort or expense. In addition, theconnection points may be mechanically and/or chemically weak(corrosion).

Accordingly, it is an object of the invention to create an extrudermethod which can produce members with duct structures having mutuallycrossing open ducts by extrusion and which does not require subsequentassembly and connection of the layers or plies of the structure with theducts.

It is another object of the invention to provide a relatively simpleapparatus for producing a multi-layer member with mutually crossingducts.

It is another object of the invention to provide an extruder nozzle formaking members extruded with crossing ducts.

It is another object of the invention to perform a multilayer memberwith crossing ducts in a single extrusion operation.

Briefly, the invention provides an extrusion apparatus comprising abarrel for movement of a flowable mass therethrough and a nozzle at oneend of the barrel for extrusion of the flowable mass therethroughwherein the nozzle has at least three segments disposed in contact witheach other and with each section having a plurality of extrusion ductsin communication with the barrel in order to extrude streams of theflowable mass therethrough. In addition, a drive means is provided formoving at least one of the nozzle segments relative to the other nozzlesegments during extrusion of the streams of flowable mass through theextrusion ducts.

The extrusion apparatus also includes a control unit for actuating thedrive means and a cutting device disposed adjacent an outlet end of thenozzle for cutting an extruded mass passing therefrom. The cuttingdevice may also be connected to the control unit for actuation insynchronism with the operation of the drive means.

In one embodiment, the segments of the extrusion nozzle are flat. Inaddition, each segment is provided with a plurality of parallellongitudinally extending portions of predetermined cross-sectional shapeto define the extrusion ducts. In this case, the longitudinallyextending portions define a plurality of spaced apart internallydisposed walls of predetermined shape with the extrusion ductstherebetween. For example, the extrusion ducts may be of rectilinearcross-sectional shape where the longitudinal extending portions are eachof triangular cross-sectional shape.

Where the longitudinally extending portions are disposed on oppositesides of a respective nozzle segment, the extrusion ducts may bepositioned angularly so as to communicate with adjacent extrusion ductsand thus define a continuous line which extends across the segment in anundulating manner. Further, the longitudinally extending portions arespaced apart to define open zones therebetween in order to selectivelycommunicate with open zones of an adjacent nozzle segment duringrelative movement between the segments. Each open zone may be of atransverse width less than a transverse width of an adjacent segmentportion.

The invention also provides an extrusion method which comprises thesteps of extruding a flowable mass of hardenable material through anozzle having at least three segments disposed in contact with eachother and with each segment having a plurality of extrusion ducts forextruding streams of the flowable mass therethrough and moving at leastone of the segments relative to the other of the segments duringextrusion of the flowable mass in order to form an extruded memberhaving extruded sections disposed in crossing relation. In this respect,one segment of the nozzle may be moved transversely of the direction ofextrusion. Also, at least two of the nozzle segments may be movedrelative to each other transversely of the direction of extrusion.

The extrusion method is conducted such that the nozzle segments may bemoved symmetrically relative to an axis or plane running at leastapproximately perpendicular to the direction of extrusion. Likewise, atleast one section of the nozzle may be moved in dependence on the valueof the extrusion velocity. Still further, the nozzle segments may bemoved with a periodic sinusoidal motion wherein the amplitude of theperiodic movement corresponds substantially to the width of the nozzleand the extruded member produced.

The operation of the extrusion apparatus is such that an extruded membercan be produced of multi-layer construction which each layercorresponding to a nozzle segment. Further, where the extrusion ductsextend in an undulating manner across the width of the nozzle segment,the resulting extruded member has a plurality of open ducts formedtherein. Due to the open zones of the nozzle segments, the ducts of onelayer are able to communicate with the ducts of an adjacent layer in thefinal extruded member.

One advantage of the extrusion apparatus is at least three nozzlesegments which abut without gaps and which are movable relative to oneanother, so giving inter alia economic savings in time and costs. Theseadvantages also apply compared with known methods using volatile orreleasable molds.

The motion of the segments of the extruder nozzle (the tool proper) mayadvantageously be controlled in dependence on the extrusion velocity.Alternatively, however, the segments of the extruder nozzle might becontrolled independently of the extrusion velocity, so that, asrequired, a large number of member structures with ducts or otherstructural features could be made from ceramic material or plasticssimply and very economically.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of the invention will become moreapparent from the following detailed description taken in conjunctionwith the accompanying drawings wherein:

FIG. 1 is a basic diagram of an extrusion apparatus embodying theinvention,

FIG. 2 is a front elevation of extruder nozzle in accordance theinvention;

FIG. 2A illustrates the segments in the extruder nozzle of FIG. 2 withextrusion ducts in a different relative position compared with FIG. 2;

FIGS. 2B and 2C show other examples of extrusion ducts of the segments;

FIG. 3 shows the rear view of the extruder nozzle shown in FIG. 2;

FIGS. 3A and 3B represents examples of velocity curves for possiblecycles of motion of individual segments and/or groups of segments ofextruder nozzles as shown in FIGS. 2 and 3, and for the extrusionvelocity;

FIG. 4 illustrates an embodiment of and extruded member with opencrossed ducts which can be produced by the method in accordance with theinvention with an extruder nozzle of the type shown in FIGS. 2 and 3;and

FIG. 5 is a part of a member with open crossed ducts.

Referring to FIG. 1, the extrusion apparatus 1 includes a barrel 13 formovement of a flowable hardenable mass therethrough, a rotatable screw11 for advancing the flowable mass through the barrel 13 and an extrudernozzle 2 mounted at an outlet 10 the barrel 13.

The material is to be extruded may for example be a ceramic material ora synthetic plastic material, such as a thermosetting plastic,thermoplastic or elastomer. For processing materials affected by heat,the extruder barrel 13 and/or extruder nozzle 2 may be provided withheater 16.

A control unit 18 is also disposed in the extruder 1 and is connectedwith a revolution counter 19 which serves to count the number ofrevolutions of the extruder screw 11.

Referring to FIG. 2, the extruder nozzle 2 is constructed with amultiplicity of nozzle segments, for example five segments 21, 22, 23,24, 25 which are disposed in contact with each other. As indicated, eachsegment 21-25 is flat and has a plurality of extrusion ducts 28 incommunication with the barrel 13 in order to extrude streams of theflowable mass therethrough. As indicated in FIG. 3, each extrusion duct28 communicates via a bore 29 with the interior of the barrel 13.

As indicated in FIGS. 2 and 3, connecting means 26, 27 are connected toalternating nozzle segments 21-25 so that the segments may be moved incommon relative to each other. As indicated, one connecting means 26 isconnected to two nozzle segments 22, 24 while the other connecting means27 is connected to three nozzle segments 21-23, 25.

As further indicated in FIG. 2, the nozzle segments 21-25 are disposedin a common frame 20 so as to be slidable relative to each other. Inaddition, the frame 20 is provided with an opening of a width V torepresent the lateral width of an extruded member 4 (see FIG. 1) whichis to be extruded. Further, the respective nozzle segments 21-25 aremovable over a stroke A as indicated in FIG. 2.

The segments 21-25 of the extruder nozzle may for example bereciprocated by means of eccentric drives 17, 17', as illustrated here.The associated regulation and control unit 18 controls the rotationalspeed of the eccentric drives 17, 17' and hence the reciprocationaccording to the rotational speed of the extruder screw 11. Adjustmentmeans 18', 18" allow the movements of the segments of the extrudernozzle 2 to be set individually within wide limits, so that members 4 ofvery varied shapes can be extruded from extrudable material.

A cutting device 31 is disposed immediately at the outlet of the nozzle2 to divide the member 4 into parts of the required type and length. Bymeans of the control unit 18, the cutting device 31 can, moreparticularly, be so controlled that on each change of direction of thenozzle movement a cut S is carried out. This results in member portionswith ducts 40 (FIG. 4) which correspond to the extrusion ducts 28 of thesegments and which extend in only one direction. As shown in FIGS. 3A,3B and 5, such cuts S take place on reversal of the direction ofmovement of the segments, i.e., in the end positions of the periodicsegment movement effected by the eccentric drives 17, 17'.

Alternatively, of course, the nozzles segments might be moved not by thetwo eccentric drives 17, 17', but by a single drive and/or other drivemeans, such as linear motors, cam discs, etc. There is moreover no needfor movements of the segments to be symmetrical. The drive for thesegments may moreover be independent of the rotational speed of theextruder screw 11, which further increases the variety of extrusionmembers 4 which can be made.

Referring to FIG. 2, the nozzle segments abut one another at theboundary surfaces 122, 223, 324, 425 without gaps. As noted above, eachgroup of first segments 21, 23, 25 or second segments 22, 24 isconnected by respective connecting means 26, 27, so that the drives 17,17' can move the groups of segments (21, 23, 25) and (22, 24) relativeto one another. The extrusion ducts 28 are here designed to extrude amember like that shown in FIG. 4, if the motion of the segments isuniform as represented in FIG. 3A. When the extrusion ducts 28 of thesegments 21 to 25 are in the illustrated positions relative to oneanother, the extrusion ducts adjoining one another form connecting zones2122, 2223, 2324, 2425.

FIG. 2A shows the groups of segments (21, 23, 25) and (22, 24) from FIG.2 with the extrusion ducts 28 in a different relative position, withoutconnecting zones.

Referring to FIG. 2, each nozzle segment is formed with a plurality ofparallel longitudinally extending portions of predeterminedcross-sectional shape, such as a triangular shape, in order to definethe extrusion ducts 28 therebetween. As indicated, the triangular shapedportions define internally disposed walls within the nozzle segment inorder to define the extrusion ducts 28, each of which is of arectilinear (rectangular) cross-sectional shape. Further, thelongitudinally extending portions are disposed on opposite sides of thesegment and are spaced apart on each side to define the open connectingzones 2122, 2223, 2324, 2425, respectively. As described below, the openzones of each segment selectively communicate with the open zones of anadjacent nozzle segment during relative movement of the segments.Further, each open zone is of a transverse width C (see FIG. 2A) lessthan a traverse width D of an adjacent segment portion. As indicated inFIG. 2a, the extrusion ducts 28 of each segment 21-25 define acontinuous line 30 which extends across the segment in an undulatingmanner in order to produce members having open crossed ducts 40 (seeFIG. 4). As indicated, the line 30 extends to and fro between theboundary surfaces 122, 223, 324, 425.

FIGS. 2B and 2C show other possible forms of the extrusion ducts whichmay, for example, in part extend rectilinearly, curvilinearly orasymmetrically. Stable self-supporting layers 21', 22', 23' ofthree-dimensional structure, which should not experience furtherdeformation after the extrusion of relatively soft material, can beproduced in this case by oblique extrusion ducts 28 which do not extendat right angles to the boundary surfaces. Advantageously, the open zonesC of the extrusion ducts in the boundary surfaces are for stabilityreasons not made too small, but they are made smaller than the closedzones D which correspond to the open ducts 40 (FIG. 4) of the extrusionmembers. As shown in FIG. 2C, these zones may also differ in a segment,for example, the zones C1, D1 of the bottom boundary surface differ fromthose (C2, D2) of the top boundary surface.

FIGS. 3A and 3B represent examples of velocity/time curves (V, T) and(V', T) respectively for the segment groups, with V₂₁, 23, 25 and V'₂₁,23, 25 respectively for the group (21, 23, 25), and with V₂₂, 24 andV'₂₁, 24 respectively for the group (22, 24), as well as the associatedextrusion velocity diagrams V_(E) (T) and V'_(E) (T). The period of thecycle of motion is designated P or P' respectively. In FIG. 3A the twosegment groups are moved in opposite directions and at a substantiallyconstant velocity. This produces members like that shown in FIG. 4 ifthe periodicity P is so selected that the length of the extruded body 4corresponds--as a result of appropriate cuts S by the cutting device31--to a half period P in which the segment velocities V₂₂, 24 and V₂₁,23, 25 are constant. This setting is particularly suitable for producingregular packings, for example for static mixers. FIG. 3B representsan--also opposite--sinusoidal velocity curve for the two segment groups,but with different amplitudes. It would also be possible, of course, tovary the extrusion velocity and/or the period and/or the pattern ofmovement. For many uses of the members 4, it is advantageous if thestructure of the ducts 40 (see FIG. 4), does not exceed an angle of forexample 45° to the direction of extrusion, in order to achieve a highmixing and homogenization effect with relatively low flow resistance.

In the portion of a member of this kind shown in FIG. 5, the amplitude Aof the segment movement moreover corresponds exactly to the width B ofthe member or of the nozzle 2. Crossed open ducts 40 then form, whichextend substantially rectilinearly through the entire member 4.

Finally, FIG. 4 shows an extruded or continuously cast member 4 in theform of a static mixer with open mutually crossing ducts 40 running fromthe interior of the member outwards to an open side boundary surface 42of the member and vice versa. The layers 21', 22', 23' correspond to thesegments 21, 22, 23 of the nozzle 2. The connection points 41, whichcorrespond to the connection points 2122, 2223 in FIG. 2, are in thisbody 4, if it is produced by the method in accordance with theinvention, particularly strong mechanically and chemically, especiallyin comparison to conventional connections made subsequently between thelayers, for example, by baking, bonding or the like.

By means of the shape of extrusion ducts 28 in the extruder nozzle 2 andthe movement and coupling of the segments 21, 22, 23, 24, 25 it ispossible to produce members of the most varied types, with the mostvaried shapes of ducts 40, in a single extrusion operation.

For example, for catalytic reactions it is a simple matter to produceadvantageous catalyst members with good mixing and reaction properties,good heat dissipation and without slip, for example by making the member4 itself produced from a porous material which acts as a catalyst, or byusing the member 4 as a supporting structure and coating it, for exampleby wash coating, with a surface layer which acts as a catalyst. For useas static mixers, members 4 advantageously have a glaze as a protectivelayer, partly to combat abrasion or corrosion and partly to render thesurface smooth and so reduce flow resistance.

We claim:
 1. An extrusion apparatus comprisinga barrel for movement of a flowable mass therethrough; a nozzle at one end of said barrel for extrusion of the flowable mass therethrough, said nozzle having at least three segments with boundary surfaces wherein the segments contact each other without gaps between the boundary surfaces, each said segment having a plurality of extrusion ducts in communication with said barrel to extrude streams of the flowable mass therethrough wherein the extrusion ducts of each segment define a continuous line that extends to and fro between the boundary surfaces; and drive means for moving at least one of said segments relative to the other of said segments during extrusion of the streams of flowable mass through said extrusion ducts.
 2. An extrusion apparatus as set forth in claim 1 which further comprises a control unit for actuating said drive means.
 3. An extrusion apparatus as set forth in claim 2 which further comprises a cutting device disposed adjacent an outlet end of said nozzle for cutting an extruded mass passing therefrom, said cutting device being connected to said control unit for actuation in synchronism with the operation of said drive means.
 4. An extrusion apparatus as set forth in claim 1 wherein said segments are flat.
 5. An extrusion apparatus as set forth in claim 1 wherein each extrusion duct is disposed angularly with respect to the boundary surfaces of said respective segment to communicate with adjacent extrusion ducts at a respective side thereof.
 6. An extrusion apparatus as set forth in claim 5 wherein said extrusion ducts of each segment define a continuous line extending across said segment in an oscillating manner.
 7. An extrusion apparatus as set forth in claim 1 further comprising a connecting means connected to at least a pair of said segments and to said drive means for movement of said pair of segments in unison relative to the remainder of said segments.
 8. An extrusion apparatus as set forth in claim 1 which comprising a screw in said barrel for advancing the flowable mass through said barrel and said nozzle and a control unit connected between said screw and said drive means for controlling the operation of said drive means in dependence of the speed of said screw.
 9. An extrusion nozzle comprising at least three segments with boundary surfaces wherein the segments contact each other without gaps between the boundary surfaces, each segment having a plurality of extrusion ducts to extrude streams of a flowable mass therethrough, wherein the extrusion ducts of each segment define a continuous line that extends to and fro between the boundary surfaces of the segment.
 10. An extrusion nozzle as set forth in claim 9 wherein each segment has a plurality of spaced apart internally disposed walls of predetermined shape defining said extrusion ducts therebetween.
 11. An extrusion nozzle as set forth in claim 10 wherein said walls define extrusion ducts of rectilinear cross-sectional shape.
 12. An extrusion nozzle as set forth in claim 9 wherein each segment has a plurality of longitudinally extending portions of predetermined cross-sectional shape defining said ducts therebetween and wherein said portions are disposed between the boundary surfaces on opposite sides of a respective segment and are spaced apart on each side to define open zones therebetween to selectively communicate with open zones of an adjacent segment during relative movement of said segments.
 13. An extrusion nozzle as set forth in claim 12 wherein each said portion is of triangular cross-sectional shape.
 14. An extrusion nozzle as set forth in claim 12 wherein said portions are disposed on opposite sides of a respective segment and are spaced apart on each side to define open zones therebetween to selectively communicate with open zones of an adjacent segment during relative movement of said segments.
 15. An extrusion nozzle as set forth in claim 12 wherein each open zone is of a transverse width less than a transverse width of an adjacent segment portion.
 16. An extrusion method comprising the steps ofextruding a flowable mass of hardenable material through a nozzle having at least three segments having boundary surfaces with the segments contacting each other without gaps between the boundary surfaces and with each segment having a plurality of extrusion ducts to extrude streams of the flowable mass therethrough, wherein the extrusion ducts of each segment define a continuous line that extends to and fro between the boundary surfaces; and moving at least one of said segments relative to the other of said segments during extrusion of the streams of flowable mass through said extrusion ducts to form an extruded member having extruded sections disposed in crossing relation.
 17. A method as set forth in claim 16 wherein said one segment is moved transversely of the direction of extrusion.
 18. A method as set forth in claim 16 wherein at least two of said segments are moved relative to each other transversely of the direction of extrusion.
 19. A method as set forth in claim 16 wherein every second segment of said nozzle is moved in unison.
 20. A method as set forth in claim 16 wherein said segments of said nozzle are moved symmetrically relative to an axis running at least approximately perpendicularly to the direction of extrusion.
 21. A method as set forth in claim 16 wherein at least one segment of said nozzle is moved in dependence on the value of the extrusion velocity.
 22. A method as set forth in claim 16 wherein at least one segment is moved with a periodic oscillating motion.
 23. A method as set forth in claim 22 wherein the amplitude of said periodic movement corresponds substantially to the width of said nozzle and the extruded member produced.
 24. A method as set forth in claim 22 which further comprises the step of cutting the extruded member at each of the end positions of said periodic movement. 